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B Jacrot

Publications and source records attributed to B Jacrot.

At least 19 recordsLinked to original sources
PubMed1995

The avian adenovirus penton: two fibres and one base.

The penton capsomer of mammalian adenoviruses consists of a trimeric, long and thin fibre inserted into a pentameric base. The avian adenoviruses possess a penton which presents another symmetry mismatch: each pentameric base is associated with two fibres. Here we have studied the morphology of the penton of CELO virus, an avian adenovirus, and we have determined the sequence of both fibres, one long and one short. The short fibre is probably associated with the base in the same way as the mammalian viral fibres and we will discuss how the long fibre could be attached. The shafts of all known adenovirus fibres consist of a series of 15-residue repeats. The avian virus fibres show a more complicated and less regular shaft repeat structure with single, double and triple repeats. The sequences of the receptor binding (head) domains of both fibres are very different from all other known fibre head domains and very different from each other, suggesting that the two fibres might bind to different receptors. The genome organization of the sequenced region is rather different from that in human adenoviruses. In particular, a region homologous to the human virus E3 region was not found at the position where it normally occurs in the human virus genome.

Amino Acid Sequence↗
PubMed1994

The penton base of human adenovirus type 3 has the RGD motif.

The gene encoding the penton base of human adenovirus (Ad) type 3 has been sequenced. The resulting amino-acid sequence has an Arg-Gly-Asp (RGD) motif located near its middle in a hydrophilic region. The same motif is found in serotypes 2, 5 and 12. This sequence was found [Wickham et al., Cell 73 (1993) 309-319] to be involved in the internalisation of Ad2 through an interaction with some specific integrins.

Adenoviruses, Human↗
PubMed1994

The fibre of bovine adenovirus type 3 is very long but bent.

The sequence of the fibre of bovine adenovirus type 3 (BAd3) predicts an extremely long structure due to a large number of 15-residue repeats in the fibre shaft, the tail and head domains being similar in size to the human adenovirus fibres. The length of the fibre was confirmed using negative-strain electron microscopy of BAd3 pentons (fibre plus penton base). The fibre was found to be bent in several discrete places and the bending sites appear to correspond with irregular repeats in the shaft. We suggest that bending of the fibre is needed for the interaction of the penton base with the secondary receptors on the cell surface.

Amino Acid Sequence↗
PubMed1992

The sequence of the genome of adenovirus type 5 and its comparison with the genome of adenovirus type 2.

We report the sequence of 7558 nucleotides of the adenovirus type 5 genome. With this sequence and previously published data, the complete sequence of this genome is now available and can be compared with the already known sequence of the adenovirus type 2 genome. These two serotypes belong to the same subgroup and sequence comparison shows 94.7% homology between the two genomes. The differences are not at all randomly distributed. Transitions between C and T and between A and G account in total for 58.3% of the differences and even for 68.6% for the genome devoid of the fiber and the hexon genes (instead of 33% expected for an equal probability of changes). In the fiber gene the transitions account for 47% of the differences. The detailed analysis of the nucleotide substitution between the two genomes suggests that the Ad2 genome could derive from that of Ad5 one, with the exception of the fiber gene which is likely to be present in Ad2 genome as a result of genetic recombination. The homology between the amino acids sequences of the structural proteins varies from 100% (proteins pVII and IX) to only 69.2% for the fiber.

Adenoviruses, Human↗
PubMed1990

Structure of adenovirus fibre. I. Analysis of crystals of fibre from adenovirus serotypes 2 and 5 by electron microscopy and X-ray crystallography.

An analysis by electron microscopy in amorphous ice and X-ray diffraction of four types of three-dimensional crystals of adenovirus fibre is presented. Fibre from adenovirus type 2 (Ad2) crystallizes in two forms depending on whether it is native or cleaved near the N terminus at Tyr17. Fibre from Ad5 also crystallizes in two forms, both of which contained fibre cleaved at Tyr17. Analysis of the packing of the fibres in each of these crystals suggests that the overall length of the fibre may be considerably longer (about 350 to 370 A) than previously reported. Crystals of cleaved Ad2 fibre are of sufficient quality to be characterized by X-ray diffraction. They are of space group C2 and cell dimensions a = 134.4 A, b = 77.6 A, c = 539.4 A, beta = 92.7 degrees. These crystals are remarkable in that, despite being monoclinic, the ab plane forms a perfect hexagonal lattice. This is explained by a trigonal packing of the trimeric fibre heads in the crystal. A similar feature is found for one type of Ad5 crystal, although the hexagonal lattice is 12% smaller. The crystals of cleaved Ad2 show very strong meridional intensity at a Bragg spacing of 4.4 A and weaker diffuse intensity corresponding to layer-lines of spacing 26.4 A. This must reflect the quasiperiodicity of the structure of the fibre shaft, which is apparent in the primary sequence. The occurrence of these features combined with the new determination of the length of the fibre (see also the accompanying paper) require a reappraisal of the cross-beta model of the fibre shaft proposed by Green et al.

Adenoviridae↗
PubMed1990

Purification and characterization of wild-type and ts 112 mutant protein IIIa of human adenovirus 2 expressed in Escherichia coli.

The expression of the protein IIIa gene from human adenovirus type 2 (Ad2) in Escherichia coli has been described previously (M. Cuillel, M. Milleville, and J. C. D'Halluin, 1987, Gene 55, 295-301). The same construct has now been used to express a protein IIIa gene from an Ad2 mutant ts 112 whose functional mutation occurs in this gene. The mutant virus is defective at nonpermissive temperatures in the latest stage of virus maturation. Both the wild-type and ts 112 recombinant proteins are produced in E. coli in an insoluble form, but are readily solubilized in urea. They have the same molecular weight in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), they sediment as a monomeric species in sucrose gradient centrifugation, and proteolytic digestion reveals a similar pattern for both proteins. Hydrodynamic studies and electron microscopy show that both proteins have an elongated shape, which can be approximated to a cylinder of 20 nm in length and 2.8 nm in diameter. The only well-established difference between the mutant and the wild-type recombinant protein is the higher solubility of the mutant.

Adenoviruses, Human↗
PubMed1990

Structural proteins of adenovirus. Expression in Escherichia coli.

The fiber proteins of adenovirus serotype 2 Ad2 and serotype 3 Ad3 and structural protein IIIa of wild type Ad2 and Ad2 ts 112 mutant were cloned and expressed in E. coli. For the expression of both fiber proteins a gene expression system based on bacteriophage T7 RNA polymerase was used. The expressed proteins constituted 1-3% of total host cell protein. Both proteins were insoluble and inclusion bodies were observed. The proteins could be purified from cellular debris by extraction with 6 M urea followed by chromatography in the presence of diminishing concentration of urea. The folding of recombinant fiber proteins was assessed by sensitivity to proteases and gel filtration. Both proteins were synthetized as trimers. Ad2 recombinant fiber has a much less compact structure than native Ad2 fiber, since on gel filtration it is excluded before the native fiber. It is also much more sensitive to chymotrypsin digestion than the native protein. Contrary to that, Ad3 recombinant fiber is much less sensitive to proteolytic cleavage and on gel filtration has the same exclusion volume as the trimeric native fiber of Ad3.

Adenoviruses, Human↗
PubMed1988

Determination of the nucleotide sequence for the penton-base gene of human adenovirus type 5.

The major structural proteins of adenovirus (Ad), which form the external capsid, are hexon, penton base and fiber. The primary structure of the Ad5 penton base has been deduced from the nucleotide sequence of the corresponding gene. It has 98.6% homology with the sequence of the analogous protein from Ad2. This result is in contrast with the significantly lower homology found for the two other major structural proteins, the hexon and the fiber.

Adenoviruses, Human↗
PubMed1987

The sequence of adenovirus fiber: similarities and differences between serotypes 2 and 5.

The amino acid sequence of the fiber from adenovirus type 5 has been deduced from the nucleotide sequence of the fiber gene. This sequence is compared with that of adenovirus type 2, a closely related serotype. We find 69% homology for the fiber protein whereas the known nonstructural proteins of these two serotypes have 99% sequence homology. A detailed sequence analysis was performed in the context of the model proposed by Green et al., [(1983), EMBO J., 8, 1357-1365] for the folding of the polypeptide chain of the adenovirus type 2 fiber. The N-terminal region, which in the virion is associated with the capsid, is identical for these two serotypes. In the shaft of the fiber the features, such as periodicity of the prolines and of the hydrophobic residues in the amino acid sequence, on which the model for the adenovirus type 2 is based are very well preserved in adenovirus type 5. On the other hand, there are large differences all along the sequence of the shaft of the fiber showing that there is a very limited homology between the amino acids in the two serotypes when they do not have a key role in establishing the structure. In the knob the homology between serotypes is 64%. These results are consistent with the differences between serotypes being confined to the exposed proteins.

Adenoviruses, Human↗
PubMed1987

Crystallization, enzymatic cleavage, and the polarity of the adenovirus type 2 fiber.

Crystals of the fiber protein of adenovirus type 2 have been grown. Analysis of these crystals (type I crystals) showed that they were composed of fiber polypeptide with a lower apparent molecular weight (60 kDa) than that of the soluble or virion-incorporated fiber (62 kDa). N-terminal sequencing revealed that the fiber polypeptide chain of 60 kDa was cleaved at tyrosine17 from the N-end. The C-terminus remained intact. Assays with protease inhibitors suggested that the spontaneous cleavage of the fiber occurring upon its crystallization was due to a cellular, calcium-dependent, chymotrypsin-like protease co-purifying with the fiber and activated during hydroxyapatite chromatography. Crystallization of fiber purified in the presence of chymostatin provided crystals of a different structure under the electron microscope (crystals of type II), composed of 62-kDa fiber polypeptide units. The 62-kDa fiber from the type II crystals, as well as the 62-kDa fiber isolated from infected cell extracts, were able to associate with the penton base in vitro to form a penton capsomer. The 60-kDa fiber has lost this capacity. The accessibility of the N- and C-termini of the fiber inside the penton structure was probed by anti-peptide sera after limited proteolysis. The results are consistent with a polarity of the fiber in which its N-terminus is oriented toward the penton base, the C-terminal domain corresponding to the distal knob.

Adenoviruses, Human↗
PubMed1986

Small-angle neutron scattering study of the ternary complex formed between bacterial elongation factor Tu, guanosine 5'-triphosphate, and valyl-tRNAVal.

The formation of the ternary complex between bacterial elongation factor Tu, GTP, and valyl-tRNAVal has been studied by small-angle neutron scattering. Titrations of the protein with amino-acyl-tRNA solutions in both H2O and 70% D2O confirm the expected stoichiometry. The molecular weight obtained for the protein alone is significantly higher than expected and can be explained by postulating a monomer-dimer equilibrium. The titration data are then internally consistent with a dissociation of the dimer on ternary complex formation. The radius of gyration for the ternary complex and the calculation of the separation of the centers of mass of the protein and tRNA components suggest a compact model for the ternary complex.

Escherichia coli↗
PubMed1986

Identification of regions of brome mosaic virus coat protein chemically cross-linked in situ to viral RNA.

RNA-protein cross-links were introduced into brome mosaic virus in situ by using the heterobifunctional agent p-azidophenylglyoxal. An improved RNA isolation method, without phenol extraction, was used to isolate RNA cross-linked with protein. RNA of the covalently linked complex was acid-digested and the oligonucleotides still attached to protein were 5'-end-labelled with 32P. The complexes were digested with trypsin and the tryptic peptides were purified by reversed-phase high-performance liquid chromatography. Amino acid analyses of cross-linked tryptic peptides revealed that out of the total 188 amino acids of brome mosaic virus coat protein only the 80 N-terminal amino acids are involved in the interaction with viral RNA. These results are discussed in connection with a predicted secondary structure of the coat protein. Both alpha helix (for amino acids 11-19) and other structures (between amino acids 20 and 80) are implicated in the coat protein-viral RNA interactions.

Amino Acids↗
PubMed1985

Effect of dinucleotides on wheat germ translation system.

The effect of ribodinucleoside monophosphates on total protein synthesis was studied in a wheat germ cell-free system, using brome mosaic virus (BMV) RNA as a messenger. Dinucleotides inhibit total protein synthesis to different extents. Of those tested the most inhibitory is CpA. The inhibitory effect of dinucleotides is due to their adverse effect on initiation and not on elongation of polypeptide synthesis. It seems that the dinucleotides complementary to the initiation codon are able to compete with the initiator tRNA during initiation of protein synthesis. The comparison of the effect exerted by different dinucleotides suggests that under conditions of the in vitro protein synthesis RNA 4 is an mRNA molecule with the initiation codon and its immediate neighbourhood being exposed.

Cell-Free System↗
PubMed1983

Structure of phenylalanine-accepting transfer ribonucleic acid and of its environment in aqueous solvents with different salts.

Thermodynamic and structural parameters were measured for brewers' yeast tRNAPhe in solution in the range of 0.1-0.9 M monovalent salt (with and without 1 mM MgCl2), pH 7.0, by small-angle neutron scattering. Partial specific volumes and preferential interaction parameters were found to be similar to corresponding values measured by more conventional means in DNA [Eisenberg, H. (1981) Q. Rev. Biophys. 14, 141-172]. There is no evidence of a large conformational change in tRNAPhe in this range, and the molecule has a radius of gyration that is the same as that calculated from the crystal-structure coordinates (23 A). Transfer RNA in solution is made up of polyion tRNA76- and 76 positive monovalent ions (in absence of Mg2+). The data show the polyion to be surrounded by a shell of solvent that is significantly denser than bulk, whose structure depends on salt conditions. In 0.1 M NaCl, it has an excess mass of approximately 85 molecules of water. This would be accounted for, for example, by approximately 850 molecules of water if their density were 10% higher than that for bulk. The radius of gyration of the dense shell is approximately 30 A for NatRNA and approximately 35 A for KtRNA. The present study shows that the solvent around tRNA is a component of its structure that must be taken into account in understanding its function.

Kinetics↗
PubMed1983

Self-assembly of brome mosaic virus protein into capsids. Initial and final states of aggregation.

The pH and ionic strength dependence of the states of aggregation of brome mosaic virus protein has been investigated by small angle neutron scattering, quasielastic light-scattering, analytical centrifugation and electron microscopy. At pH above neutrality, protein oligomers are found in dynamical equilibrium, comprising monomers, dimers and aggregates of higher molecular weight. By lowering the pH, capsids assemble spontaneously with dimensions in solution which depend on ionic strength. If formed by dialysis, they contain 180 monomers, but are 30 A larger in diameter than the native virus. If formed by pH-jump, they contain less monomers: the deficiency decreases with decreasing the final pH and the initial protein concentration. Upon dehydration for electron microscopy, capsids contract by 10%.

Capsid↗